This chapter attempts to do three things: (1) to inform the reader about current expert opinion in the area of intelligence; (2) to briefly explore the genetics and neurophysiology of intelligence; and (3) to explore the connection between cognitive factors and criminal behavior. It is contended that intelligence (as measured by IQ tests) has been unfairly dismissed by criminologists as being largely irrelevant to the explanation of criminal behavior, and that a deeper exploration of the concept will reveal a robust connection between intelligence and criminality.